Hedge funds’ speculative positions are at “pretty elevated levels” in commodities amid signs of ample inventories in some materials and concerns over the outlook for demand in China, according to JPMorgan Chase & Co.  Momentum measures and futures positioning in some assets are likely to turn “incrementally more negative,” especially for base metals, said Nikolaos Panigirtzoglou, global market strategist at JPMorgan. In March, the Bloomberg Commodity Index posted the biggest monthly loss since July. These charts show why a sell-off among hedge funds could emerge in coming months. Speculative positions in crude oil “have declined from overbought to average levels, but we...